The invention relates to an apparatus and method for guiding and cutting a continuously advancing yarn during a package doff in a takeup device of the general type disclosed in EP 0 311 827 and corresponding U.S. Pat. No. 4,948,057.
In textile machines, for example, a crimped yarn is continuously wound to a package. After the package is fully wound, it is doffed, and to this end, it is necessary to first cut the yarn, so that the full package with the loose yarn end can be exchanged for a new empty tube. During the doff, the yarn end of the continuously advancing yarn is taken in and removed by means of a pneumatic suction device. Once the package doff is completed, the yarn is caught by means of a catching device and initial layers thereof are wound on the new tube.
In the apparatus and method disclosed in the above referenced patents, the yarn is guided by means of a movable yarn guide, after the package is fully wound, outside the winding range to a suction device laterally arranged next to the winding range. After completion of the package doff, and once the new tube is ready for catching, the yarn guide is again pivoted back to the winding range. For the transfer or for catching, a transfer device deflects the yarn between the suction device and the yarn guide, and presents it to the catching device for catching.
The known apparatus and the known method have the disadvantage that at the end of the winding cycle, the loose yarn end lies on the fully wound package in an undefined manner, which makes it difficult to locate the loose yarn end in further processing.
Furthermore, the deflection of the yarn by the transfer device for catching the yarn leads to considerable loopings, which result, when compared with the winding tension, in greater tension fluctuations in the yarn. Such tension fluctuations may lead to the formation of laps on upstream feed elements.
It is an object of the invention to provide an improved apparatus and a method of the initially described type which ensures a gentlest possible guiding and catching of the yarn during the package doff and when winding initial layers of the yarn.
A further object of the invention is to ensure after cutting the yarn that the loose yarn end lies against the tie-off bead of the full package, and that the advancing yarn is threaded onto the new tube without a significant slack.
The invention distinguishes itself in that the yarn guide and the suction device are arranged within the winding range at the beginning of the package doff. In this connection, the winding range is the region on the tube, which is covered by the yarn being traversed thereover. This permits cutting the yarn with a relatively small deflection and taking it over by the yarn suction device, so that no substantial yarn tension fluctuations occur during the doffing phase. Preferably, the suction device is stationarily arranged. However, a suction device being made movable substantially parallel to the package offers the possibility of placing the loose yarn end with the tie-off bead in any desired position within the winding range.
A deflection device is provided between the yarn guide and the suction device which permits a high flexibility in the design and construction of the catching device. In addition, the deflection device prevents the yarn advancing to the suction device from being clamped between the surfaces of a new tube and the drive roll. The yarn is transferred without slacking from the full package to a new tube. A further advantage of the invention lies in that for purposes of catching, the yarn is guided on both sides of the catching device, which accomplishes a very high catching reliability.
The yarn guide and the deflection device are positioned relative to each other such that the catching device lies in the path of the advancing yarn between the yarn guide and the deflection device. This permits catching the yarn in the catching device without further auxiliary means solely by the movement of the yarn guide. To this end, the yarn is deflected only in the longitudinal direction parallel to the tube. The further, equidirectional movement of the deflection device makes it additionally possible to minimize the deflection of the yarn.
The takeup device of the present invention, wherein the tube is mounted between two clamping plates arranged on a package holder, and wherein the catching device is provided on one of the clamping plates, permits catching the yarn in a simple manner. To this end, the yarn is guided along an oblique path over the front edge of the clamping plate, so that the yarn automatically engages a catching slot arranged in the front edge of the clamping plate. In addition, the arrangement of the yarn guide, deflection device, and catching device is so advantageous that the yarn and the clamping plate perform an equidirectional movement. With that, no slack occurs and, thus, no yarn tension fluctuation in the yarn while being caught.
The deflection device consists of a movable deflecting yarn guide and a controllable drive. The drive moves the deflecting yarn guide from an idle position which is outside the path of the advancing yarn, to a deflecting position. Since the deflection device assumes a guiding of the yarn during the package doff only for a short time, the above construction of the device is very advantageous.
A transfer device guides the yarn in a simple manner from the full package into the suction device, and during the winding of the tie-off bead, as well as at the beginning of the package doff, it is possible to guide the yarn only by means of the yarn guide or only by the yarn guide and the suction device. During this time, the deflecting yarn guide remains in its idle position. No substantial deflections occur, and thus no substantial loopings. Only shortly before the new tube is brought into contact with the drive roll, will the drive activate the deflecting yarn guide for purposes of engaging and deflecting the yarn. Advantageously, the movement of the deflecting yarn guide permits coordinating it with the movement of the yarn guide for guiding the yarn into a catching range in such a manner that, for example, the activation of the drives occurs by a common control device. This permits guiding the yarn in a particularly gentle manner during the further course of the package doff. However, it is also possible to move the deflecting yarn guide in the direction of the tube edge independently of the yarn guide upstream of the driven tube.
In a particularly advantageous development of the apparatus, the deflecting yarn guide moves between its idle position and its deflecting position, and in so doing, the deflecting yarn guide traverses a path of movement transverse to the path of the advancing yarn, so that the deflecting yarn guide is able to engage and deflect the yarn in a reliable manner with its guide edge extending through the plane of the advancing yarn. The advantage of this arrangement lies in that it is possible to present the yarn from a defined position to the catching device for catching. A superposed relative movement between the catching device and the deflecting yarn guide does not exist at this time.
In a particularly advantageous further development of the apparatus, the yarn guide and the suction device are arranged in a transfer plane, so that the loose yarn end can be safely deposited on the tie-off bead of the full package. Furthermore, a simple pivoting movement of the transfer device permits guiding the yarn into the cutter of the suction device. This requires only a deflection in the transfer plane. In so doing, the gripping arm of the transfer device engages the yarn in its path of advance between the previously raised package and the yarn guide. Furthermore, this development has the advantage that when raising the package from the drive roll, the transfer device keeps the yarn safely guided in the yarn guide. The transfer plane is formed preferably within the winding range of the package and perpendicular to the axis of the winding tube and includes the tie-off wind of the package.
A vacuum connection and a cutter of the suction device are arranged in the transfer plane one following the other. This ensures that the pneumatic vacuum connection already engages the yarn before its entry into the cutter. Thus, after being cut in the cutter, the end of the advancing yarn is safely received and removed. To this end, the cutter preferably comprises a cutting blade, which cooperates with the gripping arm of the transfer device such that the cutting blade cuts the yarn clean and fast.
To guide the advancing yarn safely into the opening of the vacuum connection, the vacuum connection includes a suction opening which is slotted in the direction of the advancing yarn, and which is arranged in alignment with a cutting blade of the cutter.
In the previously described operations for doffing a package, for catching, and for winding the yarn, it is presumed that at the beginning of the package doff, the yarn is guided by an auxiliary means on a traversing yarn guide and subsequently taken over by a separate traversing yarn guide. In this connection, the yarn guide is provided preferably with a drive, which moves the yarn guide in the longitudinal direction parallel to the tube, and performs the movement of the yarn guide independently of the direction at a variable speed. In this instance, it would be possible to design and construct the drive, for example, as a linear drive.
In a very advantageous further development of the invention, the yarn guide is designed and constructed as the traversing yarn guide of a yarn traversing device. To this end, the traversing yarn guide is able to guide the yarn outside and inside the winding range in the longitudinal direction parallel to the tube. This construction has the advantage that it does not require an additional control unit for controlling the yarn traversing device. All operations during the package doff and during the catching are controlled via a controller of the yarn traversing device.
After the yarn has been caught, and after initial layers thereof have been wound on the tube, the actual winding cycle starts, i.e. the winding of the package. After the package is fully wound, the yarn is taken over by the suction device to initiate the package doff. To this end, the traversing yarn guide that guides the yarn, stops in the transfer plane. A tie-off bead is first wound on the full package, the latter having previously been raised from the drive roll. Subsequently, the transfer device guides the yarn into the suction device. Once the package has been doffed, and the empty tube is held between the clamping plates, the threadup of the yarn starts. Before the new tube is placed onto the drive roll, the traversing yarn guide and the deflection device guide the yarn out of the region of contact between the tube and the drive roll, i.e., axially beyond the end of the drive roll. The tube is placed onto the drive roll and accelerated to a rotational speed, which is required for the threadup. As soon as the rotational speed is reached, the drive of the traversing yarn guide is activated, and the traversing yarn guide guides the yarn into a catching position, in which the yarn obliquely advances over a catching plane of the catching device, for example, a front edge of the clamping plate.
The method of the present invention distinguishes itself in particular by a rapid and precise package doff. In particular, as a result of guiding the yarn upstream and downstream of the catching device, it is possible to position the yarn very accurately, so that the catching device engages the yarn reliably and without a substantial slack.
The yarn guide may be guided with the yarn to a catching position outside the winding range, so that the yarn crosses with its partial length between the yarn guide and the deflection device a catching plane of the catching device. Alternatively, for catching the yarn, the deflection device may be guided with the yarn to a catching position, so that the yarn crosses the catching plane of the catching device. These two very advantageous variants of the method permit a great freedom of design for the catching device. In addition, they make it possible to avoid unnecessary loopings of the yarn.
The use of the apparatus according to the invention in a false twist texturing machine is especially advantageous. Such machines typically comprise a plurality of side by side processing stations, with each station including means for advancing a continuous yarn serially along a heating chamber, a cooling chamber, a false twist imparting member for imparting false twist to the advancing yarn, and to a winding apparatus. Thus such machines include a plurality of winding apparatuses, which perform, without manual operation, a package doff each time after a package is wound. By being equipped with the apparatus of the present invention, the false twist texturing machine is provided with the previously described advantages.